OFFSET
1,2
COMMENTS
Inverse of Euler totient function.
According to Guy, the first even term is for 2m = 16842752 = 257*2^16. If there are only five Fermat primes, then terms will be even for 2m = 2^r for all r > 31. This was discussed in problem E3361. - T. D. Noe, Aug 14 2008
REFERENCES
J. W. L. Glaisher, Number-Divisor Tables. British Assoc. Math. Tables, Vol. 8, Camb. Univ. Press, 1940, p. 64.
R. K. Guy, Unsolved problems in number theory, B39.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
T. D. Noe, Table of n, a(n) for n = 1..10000
R. D. Carmichael, A table of the values of m corresponding to given values of phi(m), Amer. J. Math., 30 (1908), 394-400. [Annotated scanned copy]
T. D. Noe, Numbers Like 16842752.
William P. Wardlaw, L. L. Foster and R. J. Simpson, Problem E3361, Amer. Math. Monthly, Vol. 98, No. 5 (May, 1991), 443-444.
K. W. Wegner, Values of phi(x) = n for n from 2 through 1978, mimeographed manuscript, no date [Annotated scanned copy]
FORMULA
MATHEMATICA
With[{ep=EulerPhi[Range[1000]]}, Flatten[Table[Position[ep, n, {1}, 1], {n, 200}]]] (* Harvey P. Dale, Apr 10 2015 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Offset and initial term corrected Oct 07 2007
Revised definition from T. D. Noe, Aug 14 2008
STATUS
approved